Reception apparatus for telephone systems



1 Dec. 18, 1928. 1,696,024

5. B. ALLEN RECEPTION APPARATUS FOR TELEPHONE SYSTEMS Filed Feb. 21, 1924 2 Sheets-Sheer l I N VE N TOR.

' A TTORNEYJ Dec. 18, 1928.

S. B. ALLEN RECEPTIONAP PARATUS FOR TELEPHONE SYSTEMS- 2 Sheds-Sheet 2 Filed Feb. 21, 1924' N I b INVENTQR.

BY v W,

ATTORNEY! Patented Dec. 18, 1928.

STATES 1,696,024 PATNT Fries.

s'rnarrronn B. ALLEN, or CAMBRIDGE, MASSACHUSETTS.

RECEPTION APPARATUS FOR TELEPHONE SYSTEMS.

Application filed February 21, 1924. Serial No. 694,271.

This invention reiates to devices for conveniently applying means for producing an alternating potential and eliminating the passage of direct or uni-directional current to the phones. In sometclephone systems,

especially those employing thermionic tubes,

such, for example, as radio receiving apparatus, amplifiers and the like, the passage of the high potential or plate current through the phonescaiises damping of the diaphragm vibrations; and'in instances'where care is not observed in connecting the phones with due regard for polarity, tie-magnetization of the field magnets often occurs. Further, distortion of the incoming signal is a common occurrence under such conditions, especially in cases where there is no provision for regulating the distance between the pole pieces and diaphragm of the receiver,'such distor- 1 tion being electromechanical in origin@ While my invention is generally applicable to telephone receiving systems where direct or pulsating direct current is applied to the receiver, and under other varying conditions of service, it is especially adaptable for use in connection with radio receiving apparatus, amplifiers and the like WllBIGlIII'QCGPtlOD and amplification are brought about by means of thermionic tubes having the receiver con-o nee-ted in the plate circuit; though I would have it expressly. understood that I in no wise limit myself to this specific embodiment or application of my invention, which I have selected as a basis for illustrating and describing my invention. 7

My invention broadly comprlses the provision and arrangement of means, so ar ranged as to be contained Within the shell of a telephone plug or its equivalent, for preventingthe passage of direct or pulsating direct current, and for converting such pulsating currents into alternating or biased alternating current, in the telephone or loud speaker circuit.

I have found that many of the troubles inherent in certain types of telephone and amplifying systems. especially with respect to radiophone reception, originate in the damping or tie-magnetizing effects of direct current, often producing foggy tone, faulty articulation, and rattle? of the receiver diaphragm upon-reception of loud or powerful signals. In the case of tie-magnetization there occurs agradual weakening of reception as time goes on which is in many cases attributed to other parts of the apparatus.

It is the object of the present invention to provide an effective means capable of easy and convenient application by a technically unskilled user of radio apparatus, for elimi-' nating such conditions, inimical to the satis factory performance of telephone receivers, among which of course are included the variety known as loud speakers.

I shall describe certain illustrative embodiments of my invention and then point out with more particularity the essential elements ofnovelty in the annexed claims. It is j intended that the patentshall cover in the appended claims, whatevervfeatures of patentable novelty exist in the invention disclosed.

In the drawings:

Figure 1 is a diagrammatic sketch of one embodiment of the invention showing a thermionic tube amplifier with a wiring diagram of my invention attached thereto,

Figure 2 is a side elevation of a telephone connection plug, the shell of which contains the impedance coil and condenser shown diagrammatically in Figure 1;

'Figure 6 is a vertical section on the line 66"of Figure 5 showing contents of the f shell. I

.' The drawings illustrate my invention in connection with an amplifying system such as is ordinarily employed in the reception of radio signals by telephone. 1 is a vacuum or thermionic tube of the usual or any suit able type, which ordinarily is connected to a telephone receiver 6 at its input points a and b. The vacuum tube 1 in the present instance is operated by the A battery 2, supplying current to its filament 3, and the B battery/i of higher potential supplying current to its plate 5 and telephone receiver 6.

In the present common practice in radio tele phone reception and amplification the plate circuit has tcrnnnal points a and o to which the telephone is connected at 6', as shown by the dotted lines in Figure 1. Since this description is concerned only with the imn'iediate or local conditions to be met in the telephone receiver circuit a b, inwhich the plate 5 and the B battery 4 are integral parts, the specific arrangement of the grid 7 and the tube input circuit 0 (Z is to be regarded In this c escription merely indicatin suitable means whereby the plate circuit and telephone input a b is influenced and actuated. hen phones 6 connected as shown in dotted lines, the plate current passes through the phones as direct or pulsating direct current accoi .ing to the operation or excitation of the grid '7 in connection with its input circuit 0 (5. Such passage of direct current either tends to energize the pole pieces of the phones 6 further, with greater pull or damp ing load on their diaphragi is, and conseouent distortion of the signal. received, or, in cases where the phone terminals are connected at a and b in reverse magnetic relation to the phone magnets, produces a wee rening of the field generated from the pole pieces of the phones 6, considerably to the detriment oi.

eiiicient reception. Under liigh potential of the B battery 4, this may eventually'cause permanent weakening or tie-magnetization of the permanent field magnet of the telephone receiver. And even receivers havmg a separately excited field are impeded in their action by the damping load effect on the diaphragm arising from the passage of direct current through such receiver. My invention provides a means for elimi nating the passage of direct current through the phones by arranging them as at 6, and by combining therewith a condenser 9 and an impedance coil 8 (Fig. or preferably a fixed resistance 48 (Fig. 5), all arranged within the shell of the connecting plug 10, so to afford easy and simple attachment between the phones 6 and the plate circuit a b. The phones 6 are connected as shown liagramn'iatically in Figures 1 and a by the full lines, in series with the capacity 9 which serves as a stoppage condenser to prevent flow of direct current through the phones 6. The condenser9 and the phones 6, arranged in series as described, are connected across the impedance coil 8, or the fixed resistance l8 (i. e. are shunted across its terminals candf) and the impedance coil 8, or the resistance 48, is connected in the plate circuit in series with the B battery 4 and the plate 5 of the vacuum tube 1, conducting the direct current between a and 7) where the telephones have usually hitherto been connected as indicated at 6.

Referring now especially to Figures l-3, upon excitation of the grid 7 of the tube 1,

the plate current will fluctuate accordingly, and the blocking action of the impedance coil 8 in. the circuit a 2) wi l then operate to charge and discharge the condenser 9, ac-

cording to the frequency of the fluctuations.

in the plate circuit current Thus, an alternoting "voltage will be produced between the terminals 6 and 7 of the impedance coil 8;"

and the phones 6 shunted across the coil, in series with the condenser E), produce audible signals by reason of the 'ans'l'e 'ot fluctuatg or alternating potentials bi een the elements of the condenser 9 with the resultant about. esult better articulation of the re v 11s obtained; closer regulation of see distance between the pole pieces'and )hragms of the phones 6 made possible;

and, in certain instances, increased volume oi reception obtained through theability'to increase the load applied to the co-acting thermionic amplifier or vacuum tube 1, where previously such incre aedload wouldhave produced distortion of the audible signal.

An important feature of my invention in the described form is that it is so constructed as to be easily attachable without technical knowledge, as a unit, to existing systems, he- 7 so organized as to form an integral part of the connecting plug. Referring to Figure 3, the shell 11 of the plug contains the im-' pcdance coil 8 anc condenser 9 suitably con nccted to the electrodes 12 and 13, which are insulated each from the other by the insulating bushings 14 and 15, and are in the form common in standard practice and at-* tachable to the usual type of jack now employed in radio and telephone apparatus. In this construction the inside terminal f of circuit a 5,.

and by the means aforesaid Vice the coil 8 is connected. to the core 16 which acts as a conductor between the electrode 12 and the telephone binding post 17 through the clamping screw 18 and the offset support 19 for tire said binding post 17, the clamping screw 18 and offset support 19 being insulated from the cup 21 by the insulating bushings 22 and'QS. Provision is made for attaching the ot ier terminal of the telephone receiver by the binding post 20 attached to the cup 21 which in turn is conn element the condenser 9. The said telephone receivers portion of the circuit-is cornpleted by means or" he remaining and 013130? site element of the condenser 9, which isatected tonne tached to the outside terminal 6 of the wind j of the coil 8 and to the binding post 20,

the connection 9 therethrough being analogous to the point- 9 connecting with the phones 6, as shown diagrammatically in Figure 1. Thus there is combined an. impedance coil 8 having an iron core 16, and a condenser 9,'as integral parts of one apparatus unit, applicable in the usual manner of a telephone plug, to existing systems ofradio reception,

'without it being necessary for the user to understand the relations or action of the same; and a sealed closure 28 may be provided to keep people from getting at the screw 18.

Figures 4, 5 and'6 illustrate a form of the invention which is preferred on account of simplicity of construction; lower cost of manufacture; adj ustability equal or superior efiiciency; and other advantages. In this form a fixed resistance 48 takes the place of the impedance coil8 and its core 16, a simple support 56 being substituted to perform the structural function of the core. The resistance is preferably equal to or greater than the internal impedance or resistance of the thermionic tube. There is a considerable drop of electromotive force between the terminals of a high resistance 48 thus inserted in the plate circuit. The fluctuations of resistance or impedance in that part of the plate circuit which is in the thermionic tube, cause the variations of current which it has been customary to pass through the phones. The arrangement shown in Figure 4 takes advantage of the fact that a change of impedance in the tube changes the I R drop, or drop of electromotive force, between terminals 6, f, of the fixed resistance 48. As the condenser circuit 9 is in parallel with this resistance there is a fluctuation in the condenser circuit whenever the current in the plate circuit fluctuates; and this condenser fiuctuation results in, alternations of current which can be.

ance carbon disk. A simple construction is" to make this of India nk absorbed mto' a blotter, dried and compressed. Obviously it can be made otherwise; but this is easy and notably inexpensive, and when mad-e as a washeris capable of having its resistance Varied until. the desired value is attained, by merely compressing it with a screw. It is observed. in this connection that the resistance does not/change appreciably after a certain degree of compression has been reached. If made of a value ranging from 25,000 to 5-,000 ohms no difference in results has been detectible, in experiments which I have carried out.- r a In this arrangement the I R drop across the-fixed resistance produces less loss than the iron and copper losses in ordinary impedan'ce with equal volume of signal. v

lVith thermionic tubes such as are in common use for radio reception the resistance-48 hasbeen found to give satisfactory results when fiXed'at a value of 20,000 to 60,000 ohms.

In the case of a reactance or the primary of a: transformer, the impedance of the transformer or co1l-has been found to produce good results when equal to approximately 40,000 ohms at 1000 cycles, which is the rate commonlyin use for testing apparatus at voice frequencies. For the condenser, a ca pacity successfully used ranges approximately from .025 to .1 microfarad.

It will be observed that the apparatusin each of the modifications mentioned is an accessory to the telephone arranged as a unit which can be handled separately and can conveniently be interposed eXteriorly between the radio receiver, so called, and its phones, in which form it is well adapted for sale and distribution to those who already have their radio receivers. But the unit is not necessarily thus arranged and can be otherwise housed conveniently in connection with the telephone jack, or in substitution for it, in which latter case the sockets 17, 20, would be set for the convenient reception ofthe telebeing adapted for the connection to them of an external portion of the output circuit.

2. A telephone appliance comprising, in combination, a tubular shell; a telephone plug at one end thereof; telephone terminals at the other end; a centrally disposed core extending within the shell and coupling the said plug and terminals mechanically together; a

resistance between said plug and said terminals, connected to receive 'current through the plug and by-pass it around the said terminals; and a condenser arranged around the core ithin the said shell, and connected in series With one plug terminal and one telephone terminal.

3. A telephone appliance comprising, in combination, a tubular shell a. telephone plug at one end thereof; a terminal-carrying cup set in the other end; telephone terminals Within the cup; a centrally disposed core extending Within the said shell and coupling the plug and cup together; and a resistance Within the shell connected to receive current through said plug and by-pass it around said terminals,

4;. A telephone appliance comprising, in combination a tubular shell; a centrally disposed core extending therethrough; a telephone plug screwed into the core at onecend of said shell; telephone terminals at the other end of the shell; and a Washer of compressible resistance material in circuit there- With and clamped between said core and said plug; adapted for its resistance to vary ac cording to the degree which it is'comr pressed by said clamping.

5. A telephone appliancecomprising, in combination an inner and an outer tubular neeaoae p shell arranged to form an annular chamber between them; a telephone plug at one end of said shells telephone terminals at the other end; a core extending within the inner shell and coupling said plug and said, terminals together; a resistance at the base of said plug and in circuit with said plug and'terminals; and a condenser arranged in said annular chamber and connected in series with one plug terminal and one telephone ter minal. I

6. Accessory apparatus for a telephone, comprising a shell with a condenser and high fixed resistance contained therein; heads closing the ends of the shell and a core sustained between said heads; and a telephone plug com-prising insulated tip and sleeve J input ternnnals progectmg from said core; 

